Foundation Treatment for the Port River Expressway

Stage 1 of the Port River Expressway is currently under construction, at the north western suburban fringe of Adelaide. These works include approximately 4 km of new road, and three grade-separated intersections incorporating embankments up to about 10 m high. The site for the Expressway is a Holocene estuarine plain that was partly covered by mangrove swamp, and comprises normally consolidated sand and clay. Areas of uncontrolled fill, including municipal waste are also present beneath the road alignment to depths of 4 m in places.

The project challenges have required the use of a variety of ground engineering solutions, including staged embankment construction with preloading, in-situ treatment with an impact roller, stone column installation, and conventional methods of excavation and replacement. A case study of the geotechnical solutions adopted and a comparison between the predicted and actual performance of the various parts of the earthworks is presented, including an assessment of the improvement of soil stiffness by the installation of stone columns.